The present disclosure relates to an electrophotographic type image forming apparatus and an image forming method.
An image forming apparatus, such as a printer, which is capable of forming an image by electrophotography includes a developing portion. The developing portion develops an electrostatic latent image formed on an image carrier such as a photosensitive drum. For example, the developing portion has a circulation-conveyance passage through which a developer is conveyed so as to be circulated, a conveying member that conveys the developer in the circulation-conveyance passage, and an opening portion that is provided in a wall surface at the upper side of the circulation-conveyance passage. A developer supply portion that supplies the developer to the interior of the developing portion is connected to the opening portion of the developing portion.
Here, an image forming apparatus is known in which an accumulation portion for the developer is formed in the circulation-conveyance passage and below the opening portion, so that the amount of the developer supplied from the developer supply portion can be caused to follow the amount of the developer consumed at the developing portion. In this image forming apparatus, when printing with a high coverage rate is consecutively executed, the amount of the developer supplied from the developer supply portion may not follow the amount of the developer consumed in the developing portion, so that the amount of the developer held in the developing portion may decrease. In this case, the amount of the developer supplied to the image carrier may become insufficient, so that a defect called void may occur in an image formed by the image forming apparatus. On the other hand, an image forming apparatus is known which is capable of executing a developer supply mode in which, when printing with a high coverage rate is consecutively executed, the developer within the circulation-conveyance passage is circulated by using the conveying member to continue supply of the developer from the developer supply portion to the developing portion, while execution of a printing process is suspended.